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Class 701 'Aventra' trains for South Western Railway: progress updates

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Nicholas Lewis

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gabrielhj07 said:
They don’t sway as much as the BREL stuff but the ride isn’t bad.
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Sway gives you a softer suspension but comes from an era where keeping absolutely within the kinematic envelope was less of a requirement. Now we want trains that maximises internal space but the penalty is stiff suspension so you don't infringe KE. Of course seats with a bit of give would help alleviate some of the harsh ride.
 
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Goldfish62

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Nicholas Lewis said:
Sway gives you a softer suspension but comes from an era where keeping absolutely within the kinematic envelope was less of a requirement. Now we want trains that maximises internal space but the penalty is stiff suspension so you don't infringe KE. Of course seats with a bit of give would help alleviate some of the harsh ride.
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The FLEXX-Eco bogie, which all Aventras use (hence all have the same ride quality) is billed as being 30% lighter than previous designs and also reduces track wear and damage.
 
D365

D365

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Nicholas Lewis said:
Sway gives you a softer suspension but comes from an era where keeping absolutely within the kinematic envelope was less of a requirement. Now we want trains that maximises internal space but the penalty is stiff suspension so you don't infringe KE.
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And we [the railway industry] also now have software that can model this.
 
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444045

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Migsithepigsi said:
Anyone know what services will have 701s tomorrow on the Windsor/Reading/Woking branch?
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Should be a Class 701 working :

2U91 1025 Wloo to Windsor
2U92 1130 Windsor to Wloo

2U93 1253 Wloo to Windsor
2U94 1400 Windsor to Wloo

Today its U.701043 doing the honours.

Hope this helps you.
 
OneTrackMinded

OneTrackMinded

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Why was 100mph chosen on these units? As they're traveling and metro and commuter routes, surely it would have been better to stick with 75mph and dedicated more of that gearing towards acceleration. The 701s have the slowest acceleration in the Aventra family to my knowledge (0.7m/s^2 compared to 0.8m/s^2 on the 720s, 1m/s^2 on the 345s, and similar on the 710s), which doesn't make much sense considering a lot of the routes they travel on.
 
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Energy

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OneTrackMinded said:
(0.7m/s^2 compared to 0.8m/s^2 on the 720s, 1m/s^2 on the 345s, and similar on the 710s)
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720s and 345s are AC, 710s are AC and DC. DC units tend to perform worse. The 345s are still 90mph units so I'm not convinced the gearing would make them that much faster.

A decent comparison would be the 710s on DC as they are geared for 75mph.
 
WarrenTManager

WarrenTManager

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701s already accelerate very well for a DC unit. Comparing it to AC isn’t a level playing field. I’d say they are quicker off the blocks than a 707.
 
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Snow1964

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Goldfish62 said:
SWR have stated that they are deliberately "go-anywhere" units, have been cleared across the entire electrified network and could in future be used on services beyond the suburban network.
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Although there is very little on SWR network above 90mph.

But it's valid question, why 100mph, and not say 85 or 90mph which would have kept time on about 99% of services across whole SWR network.
 
43096

43096

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Snow1964 said:
But it's valid question, why 100mph, and not say 85 or 90mph which would have kept time on about 99% of services across whole SWR network.
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To give the trains' owner the maximum residual value - a 100mph unit is going to have potential for re-leasing than an 80mph units.
 
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Bald Rick

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Snow1964 said:
But it's valid question, why 100mph, and not say 85 or 90mph which would have kept time on about 99% of services across whole SWR network.
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Residual value for the lease company. 100mph is very useful elsewhere, given their AC compatibility (with some parts added).
 
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73128

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701037 looking very clean and tidy, and a sunny day. Our driver is the lady who drove the first public service.
 
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hwl

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OneTrackMinded said:
Yeah that's fair enough. Always forget how limited 750v DC is in that department.

Figure wise the 707 is supposed to be capable of 0.85m/s^2
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That is a maximum acceleration rate, the acceleration rate is non linear and varies with speed (two separate V^2 components involved in the non-linearity). The shape of the whole curve across the relevant speed range is what matters not the gradient of the steepest bit of the curve alone and the aventra curves is slightly flatter than others so while the peak value may not be as high the average is better.

With well designed modern 3phase traction motors & traction electronics and decent number of motored axles, gearing makes very little difference for max 75mph with gearing optimised for 75mph or 100mph and the excellent Aventra traction motor cooling really helps here.
 
fgwrich

fgwrich

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Goldfish62 said:
The FLEXX-Eco bogie, which all Aventras use (hence all have the same ride quality) is billed as being 30% lighter than previous designs and also reduces track wear and damage.
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To be honest, I've always found the FLEXX-Eco to be a terrible riding bogie (though it doesn't knock as badly as the CAF version). The best of those lightweight ones are the Siemens version under the 700s. At least neither oscillate as badly as the Hitachi version though.
 
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